As a practical treatment, a plurality of medicaments are mixed and administered to a patient, for example, a vitamin compound or the like is mixed in physiological saline and the solution is injected or instilled to a patient. In the case of mixing a plurality of medicaments as such, if these are previously mixed, degeneration may occur depending on the kind of the medicament. Therefore, an infusion container with multiple chambers is being used, where a plurality of medicaments having possibility of degeneration can be separately housed and can be mixed immediately before use. In some infusion containers with multiple chambers, the body is formed of a thermoplastic resin film such as polyolefin.
Such an infusion container with multiple chambers, which is formed of a thermoplastic resin film, is necessary to satisfy the requirement that the boundary portion between medicament chambers is liquid-tightly sealed in the stage before mixing a plurality of medicaments but on mixing the plurality of medicaments, the boundary portion can be easily peeled apart to open the path between chambers and the medicaments can be rapidly mixed. Therefore, a large number of studies have been made on the method for forming the boundary portion.
For example, JP-A-2-4671 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) and JP-A-2000-14746 disclose a technique of forming the portion participating in the adhesion from a specific material so as to form a readily peelable boundary portion. Furthermore, JP-A-11-169432 describes a method of coating an easily peelable coating agent on the inner surface of the boundary portion and thereby facilitating the peeling.
On the other hand, JP-A-8-24314 discloses a technique where two bars each with a seal edge having a specific shape are used in combination as a heat seal bar for use at the sealing of the boundary portion and the film is sandwiched therebetween while precisely controlling the positions of these seal edges, so that the boundary portion can have an appropriate peel strength.
However, the techniques disclosed in JP-A-2-4671 and JP-A-2000-14746 have a problem that since an easily peelable boundary portion is formed, the portion must be composed of multiple layers but a single layer film cannot be applied and the production of film costs highly. Also, the technique described in JP-A-11-169432 has a problem that a specific coating agent is necessary and the production step or production cost increases.
In the method disclosed in JP-A-8-24314, it is not essential to form a film having a multilayer structure or use a coating agent, but seal edges of heat seal bars for sealing the boundary portion must be aligned and if these positions are misaligned, the peel strength of the formed boundary portion is greatly dispersed among infusion containers each having multiple chambers. Furthermore, in the case where the heat seal bar has a narrow perforation pitch, the positions are very difficult to align and even if the heat seal temperature is maintained at a fixed temperature, the peel strength may be dispersed among infusion containers each having multiple chambers. It has been demanded to stably produce an infusion container with multiple chambers, having a desired peel strength.